1. Field of the Invention
The present invention relates to a stator for a linear motor, and in particular to a stator for a linear motor by staggered core lamination which can facilitate insulation and assembly of a stator core, can freely set an interval of an opening of the stator core, and can reduce loss of the motor by decreasing a magnetic flux density of the core.
2. Description of the Background Art
In general, a conventional motor has a flux in a three-dimensional shape, while a linear motor has a flux in a plane shape. In the linear motor, a plane-shaped movable unit performs a linear motion on a plane according to a variation of the flux formed on a plane-shaped fixed unit.
An example of the linear motor will now be explained with reference to FIGS. 1 and 2.
FIGS. 1 and 2 are a front view and a side view illustrating a structure of the conventional linear motor, respectively.
As shown in FIGS. 1 and 2, the conventional linear motor includes: an outside stator core 10 formed by laminating a plurality of core strips 1 in a cylindrical shape, the plurality of core stripes respectively internally having an opening 1a in a predetermined size; a stator coil 20 wound in a ring-shaped groove formed at an inner circumferential surface of the outside stator core formed by the openings 1a of the laminated core strips 1; an inside stator core 30 formed by laminating a plurality of core strips having a predetermined shape in a cylindrical shape, and inserted into an empty space of the outside stator core 10, having a predetermined gap from its inner circumferential surface; and a magnet paddle 50 inserted into the gap between the inside and outside stator cores 30, 10, and having a plurality of magnets 40.
The outside stator core 10 where the inside stator core 30 and the stator coil 20 are wound composes a stator of the linear motor, and the magnet paddle 50 provided with the plurality of magnets 40 forms a movable unit of the linear motor.
In more detail, the core strip 1 forming the outside stator core 10 consists of a thin plate material, and has an U-shaped pass unit 1b, and a pole part 1c extended in an inverted triangle shape at both edge portions of the pass unit 1b.
As described above, the outside stator core 10 is formed by laminating the plurality of core strips 1 in a cylindrical shape. The end portions of the pole parts 1c of each laminated core strip 1 form the inner circumferential surface of the outside stator core 10, and the outside edge portions of the pass units 1b form the outer circumferential surface thereof.
Thereafter, the laminated outside stator core 10 is fabricated by forming the stator coil 20 by winding the coil at the ring-shaped groove formed by the openings 1a of the core strips 1, and by insulating the stator coil 20.
Here, the positions of the inside stator core 30 composing the linear motor and the outside stator core 10 where the stator coil 20 is wound can be exchanged.
The operation of the linear motor will now be explained.
When a current is applied to the stator coil 20, a magnetic flux formed by the current flows along the core strips 3 of the inside stator core 30 and the core strips 1 of the outside stator core 10. The magnet paddle 50 provided with the magnets 40 carries out a linear motion in an axis direction due to an interaction force formed by the magnetic flux and the magnets 40.
However, in the stator core composing the conventional linear motor as described above, the core strips are laminated in a cylindrical shape, and the stator coil is wound at the groove formed by the openings of the core strips. Accordingly, a process of winding the coil is complicated. After winding, it is difficult to insulate the wound coil.
In addition, the conventional core strip is formed having a predetermined opening for convenience of the winding process, and thus it is impossible to change an interval of the openings in accordance to constitution of an optimal magnetic circuit.
In general, as publicly known, the density of the magnetic flux influencing on efficiency of the motor is in proportion to an amount of the magnetic flux, and in inverse proportion to a cross section of the core which the magnetic flux passes through. In the case of the stator core formed by the core strips, the core strips forming the inner circumferential surface are adhered, and thus there is no gap therebetween. However, the core strips forming the outer circumferential surface have gaps (g) of a predetermined interval. As a result, the cross section of the core is reduced as much as the gap (g), and thus the density of the magnetic flux is increased, thereby increasing loss of the motor or influencing on a size thereof.